http://www.freewebs.com/masterpikachu/ZC%20Content/Incomplete%20Quests/LOZ-Generation4.qst
When Link and a boomerang throwing enemy (such as a goriya) throw their boomerangs at the same time, the boomerang sound effect continues playing when one catches the boomerang before the other one catches it. If Link catches his boomerang first, then the sound effect set for Link's current boomerang would keep playing until you go to the active subscreen, enter a cave or throw and catch the boomerang once more. If the enemy catches its boomerang first, then the enemy boomerang sound effect would keep playing until that enemy throws and catches the boomerang once more, or until Link enters a cave, or kills that enemy while it's throwing the boomerang.